Material Selection for Servo Motors in Low-Temperature Environments

When using servo motors in low-temperature environments, material selection must carefully consider the effects of cold conditions on mechanical properties, lubrication performance, electrical insulation, and structural stability. Below are key material selection points and design recommendations:

1. Metal Structural Materials

Housing and Bearings:

Aluminum Alloy: Commonly used grades such as 6061 or 7075, subjected to T6 heat treatment to improve low-temperature toughness. Avoid ordinary cast iron (increased brittleness).

Stainless Steel: Grades like 304 or 316 offer low-temperature resistance and corrosion protection, suitable for extreme environments.

Bearing Steel: Use low-temperature-specific bearing steel (e.g., GCr15SiMn) or hybrid ceramic bearings (silicon nitride) to prevent reduced ductility in cold conditions.

Shaft Materials:

Maraging Steel (e.g., 18Ni300): High strength with excellent low-temperature toughness.

Low-Temperature Nickel Steel (e.g., 9% Ni Steel): Alternative for enhanced performance.

2. Lubricants

Low-Temperature Grease:

Base Oil: Polyalphaolefin (PAO) or ester-based oils with lithium complex or polyurea thickeners.

Recommended Products:

Mobilgrease 28 (-40°C to 150°C)

Klüber Isoflex Topas NB 52 (-60°C to 120°C)

Solid Lubricants: For ultra-low temperatures (<-60°C), consider molybdenum disulfide (MoS₂) or graphite coatings.

3. Electrical Components

Coil Insulation:

Magnet Wire: Polyimide (e.g., Kapton) or PTFE-coated wires; avoid PVC (becomes brittle at low temperatures).

Impregnation Resin: Modified epoxy or silicone resins (e.g., Dow Corning 1-2577).

PCB Substrates: High-Tg materials (e.g., FR-4 Tg≥170°C) or polyimide flexible circuits.

4. Seals and Elastomers

Seals:

Nitrile Rubber (NBR): Suitable above -40°C.

Fluorocarbon (FKM) or Silicone Rubber (e.g., modified EPDM): Required below -40°C.

Damping Components: Polyurethane (PU) or specialty silicone, with validation of low-temperature elasticity.

5. Other Critical Materials

Magnets:

Neodymium (NdFeB) magnets exhibit improved magnetic properties at low temperatures but require plating (e.g., Ni-Cu-Ni).

Samarium cobalt (SmCo) magnets for ultra-low temperatures.

Thermal Interface Materials: Low-temperature thermal grease (e.g., Bergquist SIL-Pad 2000) for motor-heatsink interfaces.

6. Design Validation

Material Testing: Conduct impact tests (e.g., Charpy), shrinkage rate, and insulation resistance measurements at target temperatures.

Assembly Tolerances: Account for differential thermal contraction (e.g., aluminum vs. steel CTE ratio ~2:1) via gaps or compensation structures.

Step Cooling Tests: Gradually reduce temperature while monitoring torque fluctuations, bearing resistance, etc.

Targeted material selection and rigorous validation ensure servo motors maintain precision, reliability, and longevity in low-temperature conditions. Practical applications should further optimize based on specific operational factors (e.g., cold-start frequency, load type).

Zhonggu Weike (Shenzhen) Power Technology Co., Ltd. is a National Specialized, Sophisticated, and Innovative ("Little Giant") enterprise specializing in the R&D, manufacturing, and application of special motors for harsh environments, including vacuum, high temperature, cryogenic, deep cryogenic, and radiation conditions. Its product range includes stepper motors, servo motors, radiation-resistant motors, vacuum modules, and vacuum gearboxes, among other standardized series.